This invention relates to a network, a network management system for managing various states of nodes incorporated in the network, and a recording medium storing a program.
As shown in FIG. 1, in a general information network system, a plurality of networks 3 each constructed by a LAN are connected via routers 4. In each network, a large number of nodes 2 are connected to a transmission line 1. In each of the networks 3, a network management system 5 may be connected.
The network management system 5 remotely monitors and manages the operating state, fault information and configuration information of a computer and communication device such as a hub and the router 4 connected to the transmission line 1 of the network 3 such as the LAN. In this specification, the router 4 and the computer or communication device such as a hub are generally called the node 2 below.
Fault information contains information indicating whether each node 2 is normally operated or stopped and information indicating the type of fault and the node 2 in which the fault occurs. Further, configuration information contains information indicating the connection relation (which is also called topology) between the networks 3 and information indicating the type of the node 2 incorporated in the network 3.
Generally, the network management system 5 stores and holds fault information and configuration information of the network 3 in a management data base. For example, as shown in FIG. 2, the network management system 5 displays the configuration information on a display screen 6 of a display device in such a configuration as a network configuration diagram 7 which will be easily understood by the operator. Further, the network management system 5 displays fault information in such a manner as to change the color of a portion indicating a corresponding node 2 according to the operating state of the node 2 on the display screen 6. Specifically, a normal node 2a is displayed in green and a fault node 2b is displayed in red.
As shown in FIG. 2, the internet protocol (IP) address and the host name which is part of the name of the node 2 are displayed for each node 2 on the screen 6.
In order to display the above network information, it is necessary to collect the newest configuration information and fault information described before. There are various methods for collecting the newest configuration information and fault information by use of the network management system 5.
For example, a basic method in which the operator inputs the configuration of the network 3 via an input screen can be considered.
However, the above setting operation is extremely complicated, and therefore, a method in which the network management system 5 automatically collects the information directly from the network 3 is proposed. For example, the network management system 5 detects one node 2 on the network 3 by use of proper means and registers the IP address and the name information containing the domain name and host name relating to the node 2 into the management data base.
Then, the network management system 5 makes an inquiry about configuration information of another node 2 to the registered node 2 by use of the IP address. The node 2 receiving the inquiry from the network management system 5 sends the IP address and the host name of another node 2 with which it communicated in the past to the network management system 5. Thus, the network management system 5 sequentially traces the nodes 2 in a preset order to obtain the current network configuration diagram 7 shown in FIG. 2 (U.S. Pat. No. 5,185,860).
However, the network management system 5 using a method for sequentially tracing the nodes 2 connected to the transmission line 1 of the network 3 in a preset order has the following problems.
As shown in FIG. 1, a preset number of IP addresses are stored (pooled) in a DHCP (Dynamic Host Configuration protocol) server 8 used as an IP address assignment section provided in the network 3 instead of fixedly assigning the IP addresses to the respective nodes 2 connected to the transmission line 1 of the network 3. The network 3 for assigning one of the IP addresses pooled in the DHCP server 8 to the node 2 of request source in a specified preset lease period T only when an assignment request is issued from the node 2 is put to practical use.
The node 2 which has received the IP address is permitted to communicate with the nodes 2 of its own network 3 and the nodes 2 of another network 3 via the router 4 by use of the IP address. In a case where the node 2 uses the same IP address after the elapse of the lease period T, the node 2 can continuously use the IP address if it issues an update request (lease rewriting request) for the IP address assignment to the DHCP server 8.
Thus, if the DHCP server 8 manages in a lump the IP addresses used in the network 3, the address assignment process and address release process effected when the node 2 is temporarily connected to the transmission line 1 of the network 3, when the node 2 is eliminated from the network 3 or when the node 2 is not used for a long period of time can be extremely simplified. Particularly, in a state in which the mobile computing system is being developed, it becomes important to quickly grasp configuration information of the node 2 newly connected to the network 3 and deal with the node as a to-be-managed object.
However, in the network management system 5, since configuration information items of the nodes 2 are collected by sequentially tracing the nodes 2 in a preset order, for example, a large amount of processing time is necessary to collect the IP address of a node 2 newly added to the network 3. As a result, there may occur a problem that configuration information of the nodes 2 constructing the network 3 displayed on the display screen 6 of the network management system 5 is different from configuration information of the nodes 2 of the actual network 3.
Next, a case wherein the node 2 is eliminated from the network 3 or the operation thereof is stopped for a long period of time will be explained.
Basically, the network management system 5 periodically sends a diagnosis signal to the nodes 2 and determines whether each node 2 is operated or stopped based on whether a response to the diagnosis signal is obtained or not. In a case where the operation of the node 2 is interrupted, information of the corresponding node 2 in the management data base is deleted when a preset permissible period has elapsed.
Next, the node 2 to which the IP address is assigned by the DHCP server 8 is considered. It is meaningless for the network management system 5 to manage the IP address which is assigned to the node 2 after the operation of the node 2 is interrupted, the lease period T of the IP address is expired and the IP address is released by the DHCP server 8.
After the IP address is released from one of the nodes 2, it may be assigned to another node 2 which attempts to newly acquire an IP address in the DHCP server 8. Therefore, it is a problem that the network management system 5 manages the released IP address as the IP address of the node 2 to which the released IP address was previously assigned.
That is, even if the IP address is assigned to another node 2, the IP address is dealt with as the IP address of the previous node 2 until the node 2 is detected by the network management system 5. As a result, since information on the network management system 5 does not coincide with the status on the actual network 3, the manager may misunderstand the situation.